1. Field of the Invention
The present invention relates to a mounting structure of a component to an exhaust pipe, the structure being suitable to be used in a case that a material whose high-temperature strength is low is used for an exhaust pipe.
2. Description of the Related Art
In a vehicle such as a motorcycle, a low specific gravity material such as titanium and a titanium alloy is sometimes used for an exhaust pipe in order to save weight. For example, Patent Document 1 discloses a configuration in which a catalyst pipe is formed of stainless steel and an exhaust manifold connected to the catalyst pipe is formed of titanium or a titanium alloy, whose specific gravity is smaller than that of the catalyst pipe.    [Patent Document 1] Japanese Laid-open Patent Publication No. 2007-51571
In a vehicle to which an engine is mounted, an air-fuel ratio sensor is sometimes mounted to an exhaust pipe in order to perform air-fuel ratio feedback control, for example. More specifically, the air-fuel ratio sensor is screwed into a boss provided in a predetermined position of the exhaust pipe and a sensor portion at a front end of the air-fuel ratio sensor is inserted into the inside of the exhaust pipe.
In this case, if the exhaust pipe is formed of titanium or a titanium alloy, it is necessary that the boss provided in the exhaust pipe is also formed of titanium or a titanium alloy because of difficulty in welding titanium and a dissimilar metal. However, since a screw portion formed in the boss for screwing the air-fuel ratio sensor thereinto is exposed to high-temperature gas, usage of titanium or a titanium alloy, which is low in a high-temperature strength, for the boss leads to a possibility that the screw portion formed in the boss is softened and that torque down occurs.